Multi Device Viewer

A local-first Chrome MV3 extension for responsive website testing across mobile, tablet, laptop, desktop, watch, and TV viewports without leaving the current tab.

Click the extension icon on any page and a full-screen mobile preview and device simulator opens on top — no new tabs, no navigation away. Close it and the page is exactly as you left it.

Features

• Full-screen overlay on the current tab — stays on the same page.
• Up to four device previews side by side with resizable panels.
• Collapsible left sidebar with controls; per-card device switcher.
• Device catalog covering phones, tablets, laptops, desktops, watches, and TVs, including newer 2025 iPhone profiles.
• Device search, filters, favorites, recents, and custom viewport creation.
• Built-in layout presets plus saved custom presets with JSON import/export.
• Per-device orientation, zoom, fit, and reload controls.
• Global URL bar to send a new page to every active device preview.
• Inspect mode for quick responsive QA overlays.
• Dark mode for low-glare testing.
• Realistic device frame shells (phone, tablet, laptop, desktop, watch).
• Chrome context-menu shortcut to open the current tab directly in Multi Device Viewer.
• "Capture & Annotate" — captures the full simulator view and opens a built-in annotation editor.
• Annotation tools: pen, rectangle, arrow, text (with font size picker), and crop.
• Crop bakes annotations into a new canvas; copy to clipboard or download locally.
• All screenshots and annotations stay on your machine — nothing leaves the browser.

Development

npm install
npm run dev

Load the unpacked extension from .output/chrome-mv3/ in Chrome developer mode (chrome://extensions).

Build

npm run build
npm run zip

The production zip lands in .output/.

Release

Manual Chrome Web Store releases use the Chrome Web Store Release GitHub Actions workflow. See docs/chrome-web-store.md for listing copy, required GitHub secrets, OAuth setup, and the release checklist.

Privacy

The extension is entirely local. It does not collect data, contact a backend, or use analytics. See docs/privacy-policy.md for the full policy.